1. Field of the Invention
The present invention relates to a method for transmitting data from wireless keyboard, that is an input device of personal computer, having track-ball, and more particularly relates to a method for transmitting data of wireless keyboard having track-ball that is able to transmit keyboard data and track-ball data more effectively at the same time.
2. Description of the Prior Art
A keyboard device and a mouse device are typical input devices of personal computer. And recently, with highly developed technologies, in order to solve the problems that occur because of keyboard device and/or mouse device being wired to computer main body and the cost problems and the installation problems that occur because of a mouse and a keyboard are independently installed from main body, a wireless keyboard device having track-ball, that combines a mouse into a keyboard(73) in a track-ball(732) type as described in FIG. 7 and performs a data transmission with personal computer(72) by wireless signals such as infrared or high-frequency signals, is being developed.
The wireless keyboard device mentioned above, as described in FIG. 7, has advantages such as the installation and operation become simple because wiring cable is not needed for data transmission to computer(72), and numbers of users are able to use a computer simultaneously by connecting numerous keyboards to a computer. However, compared with a wired keyboard device, it has a handicap that key-scan data and/or track-ball data could be easily miss-transmitted by surrounding noises and/or the other causes.
FIG. 1 is a block diagram illustrating a general data transmission method of wireless keyboard. It carries out a scanning by a certain period and transmits the scanned data in a packet unit. The transmission period(T1) of said packet is, for example, 25 msec, and a packet comprises a leader signal(in other words, it is called preamble signal) that notifies data transmission to computer main body to be synchronized, and the 4 bytes of data, transmitted consecutively after said leader signal, that contain keyboard and/or track-ball data.
In general, the data of wireless keyboard is transmitted by well-known 4 PPM(Pulse Position Modulation) method.
In the prior art, as described in FIG. 2, a code of 0001110 is transmitted as a leader signal using 7 chips. Here, because the size of a single chip is 321.4 xcexcm, the leader signal has the size of 2.249 ms( 321.4 xcexcmxc3x977=2.249 ms).
In general, the main function of a leader signal is to make receiving part(of personal computer) to acknowledge that the following data is to be received and to make an input device and the main body to be synchronized easily. In case that a leader signal becomes larger as described above, it has an advantage, in the receiving part, that it has very strong noise-resistance, however, in the transmitting part that has to transmit data consecutively with designated period, it has problems that data handling becomes difficult and current consumption becomes large because of the large size of the signal.
In addition, for the case of wireless keyboard having track-ball, track-ball data and keyboard data should be transmitted together. In this case, if the data structures of keyboard data and track-ball data are different from each other, receiving part should be constructed to be able to handle the two different formats, and thereby the program size of the receiving part becomes large and it becomes inefficient.
The present invention relates to a method for transmitting data of wireless keyboard having track-ball, which transmits track-ball data and keyboard data more effectively, and thereby simplifies the processes of receiving part and reduces the current consumption of keyboard device. The data transmission method of wireless keyboard having track-ball in accordance with the present invention transmits a leader signal composed of five chips comprising the first three consecutive low signals and the following high signal and low signal, thereafter transmits data that contains track-ball data and keyboard scan data recorded in the same data format, and, instead of check-sum code, allocates the complementary value of the code value of the third byte(Byte3) into the fourth byte(Byte4) and transmits it so that the transmission error can be checked by simply comparing the third byte and the fourth byte, and thereby reduces the current consumption of keyboard device and simplifies the receiving processes of computer.